I'll have to look for the Hellwig number, it's been a few years, but I have it.

Yes, they are supposed to be mounted underneath the spring. But with only a little mod or two, they will go over the rear segment. And they are strong enough that the rear clamp does not need to pull the helper leaf down against the leaf spring.

It will be an inch or so above the leaf allowing height adjustment.

I have successfully used this on several cars after trying re-arching and buying new springs. The helper leafs are the only thing I have tried that allows me to have complete control over the height and right to left level and weight distribution.

The Cuda can pull a 1.5 60ft, so I haven't found a down side to the helper springs yet.

I will follow up with the Hellwig number and try to post a shot of them on the Cuda. Probably tomorrow.